1. Field of the Invention
This invention relates to coaxial flue piping systems for factory built, direct vented, gas burning fireplaces or stoves having a sealed combustion chamber that vents either through a wall or a roof. In particular, this invention relates to coaxial pipe assemblies that lend themselves to a quick, easy, and clean method of connection to form a complete, coaxial flue piping systems.
2. Background Information
Fireplaces which open into a room are commonly found in homes to provide a highlight in aesthetic value and/or meet the need for space heating. These conventional fireplaces take the air needed for combustion from the hot or cold air in the interior living environment of the house. Other home appliances such as running kitchen exhaust fans and toilet exhaust fans draw from this supply of air as well. Normally, this living space air gets replaced by the regular infiltration of outside air through cracks around windows and doors.
In an effort to build more energy efficient houses, the housing industry now builds homes and multi-family units that have essentially become air tight. These air tight homes have led to a reduction in the infiltration of outside air. Under circumstances such as running kitchen exhaust fans and toilet exhaust fans, not enough outside air infiltrates the home to maintain the operations of all the home appliances that utilize air. These various appliances can create a slight negative air pressure in the house which makes it more difficult for a conventional fireplace to work at its optimum level. In some cases, the lack of infiltrated air starves the conventional fireplace for air.
Gas burning fireplaces and stoves also are commonly found in homes to provide a highlight in aesthetic value and/or meet the need for space heating. Unlike conventional fireplaces, direct vent fireplaces do not need to take air from the living environment. Rather, direct vent fireplaces are sealed in the front with fresh air being provided from the outside by a chimney formed from a coaxial pipe system disposed between the direct vent fireplace and a wall or the roof. Because of this significant difference between conventional fireplaces and direct vent fireplaces, there is a shift toward using direct vent fireplaces.
Coaxial flue systems used to replenish fresh air to and exhaust waste gases from conventional fireplaces are known. For example, U.S. Pat. No. 4,607,665 belonging to the assignee of the present invention discloses a mechanical spacer for snapping and holding an inner pipe fixed in place within an encasing outer pipe in a multiple wall pipe assembly. The spacer both functions in place of a bracket in a double wall-chimney pipe assembly and provides several nibs that are used to snap fit one coaxial pipe assembly into an adjacent coaxial pipe assembly. Since the unitary spacer requires no external hardware nor requires welding, screwing, riveting or the like step in the manufacturing or assembly of the pipe assembly, a complete pipe assembly consisting of the inner pipe, outer pipe, and the spacer facilitates the ease in connecting together additional such pipe assemblies to form a complete pipe system.
Art that relates to "fireplace" and "coaxial pipe" includes U.S. Pat. Nos. 5,647,340, 5,479,916, 5,218,953, 4,082,322, and 4,060,068. Patents that reference patent U.S. Pat. No. 4,607,665 belonging to the assignee of the present invention include U.S. Pat. No. 5,509,696 (Connector with spring retainer); U.S. Pat. No. 5,468,026 (Spacer clip for chimney); and U.S. Pat. No. 4,951,714 (Means for vertically supporting a segmented high-temperature internal conduit). Patents that relate to direct vent fireplaces include U.S. Pat. Nos. 5,782,231, 5,715,808, 5,669,374, 5,471,973, and 5,392,760 (Direct vent fireplace); U.S. Pat. No. 5,603,312 (Direct vent wood burning fireplace); U.S. Pat. No. 5,590,641 (Adaptor for installing flue liners to direct vent fireplace inserts); U.S. Pat. No. 5,562,088 (Termination device for horizontal direct vent gas fireplaces or the like); U.S. Pat. No. 5,267,552 (Direct vent gas fireplace); U.S. Pat. Nos. 5,076,254 and 5,016,609 (Direct vented multi glass side fireplace).
To form the chimney of a direct vent fireplace, most coaxial flue system require several coaxial pipe assemblies to form a complete pipe system. Certain installations of direct vent fireplaces require that the direction of the chimney change. This necessitates the installation of elbow coaxial pipe assemblies to form bends in the chimney.
Known coaxial pipe assemblies do not lend themselves to quick, easy, and clean methods of connecting multiple coaxial pipe assemblies to form a complete pipe system. Those assembling multiple coaxial pipe assemblies into a complete pipe system must handle both an inner and outer pipe. This double handling of the pipes is made especially difficult due to the minute amount of piping rotational alignment adjustments necessary to meet unique field conditions. For example, practicing U.S. Pat. No. 4,607,665 requires two people: one to hold the two joining inner flue pipes steady while the other rotates the a first and second outer flue pipe until the nibs of the pipe spacer project past their respective openings and snap into a grove in the second outer flue pipe. Moreover, on aligning one coaxial pipe assembly with an adjacent coaxial pipe assembly, many screws are typically used at each pipe joint to maintain the integrity of each coaxial pipe assembly connection against possible disconnect as required by building codes.
Once the complete pipe system is assembled, the caulking requirements do not lend themselves to a clean installation. For example, caulking is required for the coaxial pipe system of U.S. Pat. No. 4,607,665. As shown in FIG. 7 of U.S. Pat. No. 4,607,665, male end of the inner flue pipe is inserted into the female end from above the female end. As smoke travels upward within the inner flue pipe, the smoke is forced upward into the space between the male end and the female end of U.S. Pat. No. 4,607,665. Since the ball and cup seating design of the male end ridge coming to rest on the female rim cannot be made air tight, the ball and cup seating design is not sufficient for restricting smoke to the interior of the inner pipe. Thus, the inner flue pipe of U.S. Pat. No. 4,607,665 must be caulked to prevent the leakage of smoke from the inner flue pipe.
Thus, there is a need for a coaxial pipe assembly that overcomes these disadvantages relating to known complete pipe systems for fireplaces.